Payers like Express Scripts are not the only ones worried about the rising prices of cancer drugs—patients are also airing their grievances, generally through social-media platforms like Twitter and online discussion boards, according to a new report from the IMS Institute for Healthcare Informatics.

The annual cancer report found that cancer patients rely on social media to share financial frustrations, medical advice and treatment information. They largely use Wikipedia and Google for information about their cancers.

Prostate-cancer patients were the most visible cancer patient population, and researchers wrote that their online behavior follows a pattern that matches their stage of treatment. About a third of online conversations from just-diagnosed prostate-cancer patients focus on biomarkers, 67% of conversations by patients about to undergo treatment focus on care options and 43% conversations among of patients living with prostate cancer are about costs.

Brands looking for feedback should generally be on Twitter—especially for discussions about prostate-cancer drugs Jevtana, Provenge, Taxotere, Xtandi and Zytiga. IMS said Facebook and clinical trial websites are also resources, but researchers said patients do not use them as much for discussions about a particular drug.

Seeing what patients are saying about their treatments online could provide drugmakers with a critical marketing edge. Some of that information could help companies strengthen their product strategies when creating materials for accountable care organizations, oncologists and other healthcare professionals.

Researchers noted that the concept of value is going to become an increasingly hard one for pharma to make, despite an evolution in cancer treatments and increased screening rates. About two-thirds of Americans with cancer now have a five-year survival rate as compared to the 50% rate of the 1990s.

Competition is just one element that makes it difficult for payers to assess a cancer medication’s value. Researchers wrote that a drug’s ability to be used across multiple cancers may also make it difficult to assess a treatment’s value because a drug will not necessarily have the same impact in each type of cancer.

This appears to run counter to drugmakers’ desire to create therapies that can used with multiple drug regimens across indications. IMS said although payers may be able to understand the clinical value of a treatment, they track the costs of discrete treatments and do not look at the value of a therapy used to treat different cancers or in combination with other drugs. This problem is expected to grow—IMS said 48 of the 88 cancer drugs used in 2014 were for multiple indications. IMS anticipates that mixing and matching treatments for effective outcomes is a trend that will continue across cancer indications over the next six years.

Collaborations like the one in which Eli Lilly will explore how its cancer medication Alimta works when paired with Merck’s PD-1 inhibitor Keytruda are common. But IMS researchers noted that cross-industry partnerships will make it harder to negotiate prices because companies may constrain one another’s flexibility to negotiate when it comes to making deals with payers. Some companies have already tried to avoid this. IMS said Roche, Bristol-Myers Squibb, AstraZeneca and Johnson & Johnson’s Janssen are concentrating on in-house drug combinations, which will give them negotiation freedom once the drugs are approved.

The money at stake is considerable: IMS said the monthly cost of a cancer treatment has jumped 39% in the past decade, to $5,900. IMS said the eight newest drugs cost even more, with prices ranging from $7,200 to $13,700 per month. Adding to the financial impact is that the course of treatment for some of the newer cancer regimens is expected to last a year or longer.

Further, the oncology drug market is expected to be worth $550 billion in five years. The IMS report found that $100 billion was spent on cancer medications worldwide in 2014, up from $75 billion in 2010.